Photoelectric type weft sensing process and weft sensor

ABSTRACT

Interception of light, which is emitted by a light emitter positioned on one vertical side of the warp sheet, by the weft at the moment of picking motion is sensed by a light receiver positioned on the other vertical side of the warp sheet while cutting off luminous noises by the warp sheet and, after the photoelectric conversion, corresponding electric signals are given to a discrimination circuit so that the absence of weft at the time of the picking motion will cause instant interruption of the loom running.

United States Patent [191 Suzuki July 16, 1974 PHOTOELECTRIC TYPE WEFT SENSING PROCESS AND WEFT SENSOR [75] Inventor: Toshiyuki Suzuki, Nara-ken, Japan [73] Assignee: Enshu Limited, Skizuoka-ken, Japan [22] Filed: Nov. 14, 1972 [2]] Appl. No.: 306,206

[30] Foreign Application Priority Data Nov. 16, 197] Japan...; 46-92050 Nov. 16, 1971 Japan 46-92051 [52] US. Cl. 250/561, 139/370 [51] Int. Cl. G01n 21/30 [58] Field of Search 250/219 WE, 219 8,219 F; 139/370, 371, 372, 377, 353, 354, 355

[56] References Cited UNITED STATES PATENTS 3,139,911 7/1964 Breitmeier 139/370 3,385,971 5/1968 Fertig 250/219 WE 3,489,910 1/1970 BBhme 250/219 S 3,532,138 10/1970 Schlappi 139/370 3,590,882 7/1971 Pfarrwaller 139/370 3,608,590

9/1971 Hohenermn: 139 370 Primary Examiner-James W. Lawrence Assistant Examiner-D. C. Nelms [57] ABSTRACT Interception of light, which is emitted by a light emitter positioned on one vertical side of the warp sheet, by the weft at the moment of picking motion is sensed by a light receiver positioned on the other vertical side of the warp sheet while cutting off luminous noises by the warp sheet and, after the photoelectric conversion, corresponding electric signals are given to a discrimination circuit so that the absence of weft at the time of the picking motion will cause instant interruption of the loom running.

30 Claims, 36 Drawing Figures PAIENTEBJUL 1 51974 sum 03 or 16 PATENTED JUL 1 s 1974 SHEET 0 0F 16 v UUJMOOFOIL mmZwowm PIG-4 N mt Pmmrznwu wn 3824.401

sum us or 16 Fig. Fig. 85

FATENTEU JUL 1 6 I974 SHEET 08 0F 16 1 PHOTOELECTRIC TYPE WEFT SENSING PROCESS AND WEFT SENSOR The present invention relates to a photoelectric type weft sensing process and a weft sensor. More particularly the invention relates to a process for sensing weft during picking motion by light emission across the warp sheets and also to a weft sensor for carrying out such a process on weaving looms.

Even in the conventional art, a mechanism called the center fork has been used in the weaving field in order to sense the absence of the weft and/or incorrect insertion of weft at the time of the picking motion. In the case of this mechanism, sensing of the weft is carried out through direct contact of the fork with the weft under picking. Such direct contact of the fork with the weft tends to damage the weft and to develop undesirable thread loops on the surface of the fabric obtained therefrom. In addition, the fabric surface is liable to be soiled by flying machine oil and damaged by the fork.

A principal object of the present inventionis to provide a process and a sensor for carrying the weft sensing work on looms in a photoelectric manner without direct contact of the sensing terminal with the weft under picking.

Another object of the present invention is to provide a process and a sensor for carrying out the photoelectric weft sensing work with increased reliability while eliminating luminous noises caused by warp sheets.

In order to attain these objects, the weft sensing light beams of the present invention are emitted from a light emitter located on one vertical side of the warp sheet(s) at a position about the middle of the lathe length, the light beams so emitted being advanced across the warp sheet(s) and the course of the weft under picking so as to be received by a light receiver located on the other side of the warp sheet(s). The light beams so received are converted into corresponding electric signals by one or more photoelectric cells incorporated within the light receiver by a filtering operation by a weft-image selector mechanism and the electric signals so produced are given to a discrimination circuit. The running of the loom is interrupted only when the absence of the weft at the time of picking motion is sensed.

Further features and advantages of the present invention will be made clearer from the following descrip tion, reference being made to the accompanying drawings, in which:

FIG. 1 is a front plane view of a loom equipped with the photoelectric type weft sensor of the present invention;

FIG. 2 is a side plane sectional view of the basic embodiment of the photoelectric type weft sensor of the present invention;

FIG. 3A is a side plane sectional view of the light receiver used in the weft sensor of the present invention and provided with the first embodiment of the weftimage selector mechanism;

FIG. 3B is a bottom plane view of the light receiver shown in FIG. 3A;

FIG. 4 is a bottom plane view of the second embodiment of the weft-image selector mechanism used in the weft sensor of the present invention;

FIG. 5A is a side plane sectional view of the light receiver used in the weft sensor of the present invention and provided with the third embodiment of the weftimage selector mechanism;

FIG. 5B is a bottom plane view of the light receiver shown in FIG. 5A;

FIG. 6 is a perspective plane view of a typical embodiment of the mechanism for producing synchronizing pulses in the weft sensor of the present invention;

FIG. 7 is a block diagram showing the structure of an embodiment of the discrimination circuit used in the weft sensor of the present invention;

FIGS. 8A and 8B are explanatory top plane views of the lathe and its related arrangement at different mornents in the crank cycle;

FIGS. 9A and 9B are graphic drawings showing convertion in the wave-form of signals processed through the discrimination circuit shown in FIG. 7;

FIG. 10 is a perspective plane view of another embodiment of the weft sensor of the present invention and its related loom parts;

FIG. 11 is a vertical cross sectional plane view of the weft sensor shown in FIG. 10;

FIGS. 12A through 12D are explanatory top plane views of several modifications of the weft sensor shown in 'FIG. 10;

FIGS. 13A and 13B are explanatory views showing two different running fashions of the weft course;

FIGS. 14A and 14B are graphic drawing showing two different-production modes of wave-forms indicating the presence of weft;

FIG. 15 is a partly sectional side plane view of still another embodiment of the weft sensor of the present invention;

FIG. 16 is a sectional sideplane view of a light receiver used in the weft sensor shown in FIG. 15;

FIG. 17 is a top plane view of the light receiver shown in FIG. 16;

FIG. 18 is a block diagram of one example of the discrimination circuit used in combination with the weft sensor shown in FIGS. 15 through 17;

FIG. 19 is a graphic drawing showing conversion in the wave-form of signals processed through the discrimination circuit shown in FIG. 18;

FIG. 20 is a partly sectional side plane view of a still further embodiment of the weft sensor of the present invention;

FIG. 21 is a sectional front plane view of the weft sensor shown in FIG. 20;

FIG. 22 is a top plane view, partly omitted, of the weft sensor shown in FIG. 20;

FIG. 23 is a perspective plane view of a still further embodiment of the weft sensor of the present invention;

FIG. 24 is a partly sectional side plane view of a modification of the embodiment shown in FIG. 23;

FIG. 25 is a partly sectional top plane view of the main part of the arrangement shown in FIG. 24;

FIGS. 26A and 26B are top explanatory views of the weft sensing operation using the arrangements shown in FIGS. 23, 24 and 25.

The entire structure of a loom equipped with the basic embodiment of the photoelectric type weft sensor of the present invention is shown in FIG. 1 in a somewhat simplified illustration, the structure being basically the same as that of ordinary looms. Briefly mentioning the structure, a tappet shaft 2 and a rocking shaft 3 extending laterally transverse the loom width and are carried on both sides by side frames 1 of the loom, the rocking shaft 3 carrying lathe swords 4 in a to-and-fro swingable disposition. The lathe swords 4 carry at their top ends a lathe 6, along the upper face of which a shuttle 7 reciprocates for insertion of weft 8. Inthe drawing, the weft 8 is illustrated by a chain and dot'line. This reciprocal movement of the shuttle 7 is effected by pickers 9 disposed to tops of corresponding picking sticks 11 which are mounted on both end parts of the rocking shaft 3 and operated for the picking-motion by associated picking bands 12. A reed cap 13 is mounted'above the lathe 6 in order to accommodate multipleside-by-side aligned reeds 14 between them. In

described structure of the loom. A recess 101 is formed in the upper face of the lathe 6 at a position substantially midway of the lathe length. A light emitter 102 is arranged within the recess 101 with its convergent lens 103 facing upwardly. This light emitter 102 is internally provided with a suitable light source such as an electric lamp or a light emitting diode. The light produced by such light source is converged by the lens 103 and, in the form of a beam X, advances towards the lower face of the reed cap 13 across the running path of the shuttle 7. Alight receiver 104 is disposedto the lower face of the reed cap 13 at a position where the beam X from the light emitter 102 arrives. This light receiver 104 is providedwith a weft-image selector mechanism 106 on its end facing the convergent lense 103 of the light emitter 102. Further, the light receiver 104 is internally provided'with a photoelectric cell 107 whichis connected to a later described discrimination circuit via electric connections 108.

, In a preferred embodiment, a brush 19 is fixed to the breast beam 21 of the loom, projecting rearwardly so that the surface of the lens 103 of the light emitter 102 can be cleaned by the brush 19 at every swinging cycle of the lathe 6. In this connection, however, it should be understood that the provision of such a cleaning brush is quite optional.

The weft-image selector mechanism 106 incorporated in the light receiver 104 has a function of clearly picking up the weft-images in contrast to the warpimages which are always received by the light receiver 104. In other words, for further operation of the weft sensor of the present invention, only the weft-images are selected outof all types of images arriving at the light'receiver 104.

The first embodiment of the weft-image selector mechanism is shown in FIGS. 3A and 3B, in which the light receiver 104 includes: a casing 109 having a cavity; the photoelectric cell 107 incorporated within the casing 109; the electric connection 108; and; a bottom lid 111 disposed to the open bottom end of the casing 109. This bottom lid 111 is provided with 'a long straight slit 112 which runs in the direction of the weft inserting courses 8a and 8b as shown in FIG. 3B. In the present embodiment, the weft-image selector mechanism 106 is in the form of this bottom lid 111 having 4 the long slit 112. By provision of this straight slit 112, useless images such as the warp-images are'effectively shut out and only the necessary weft-images are skillfully picked outwith excellent clearness. Dimensions of the slit 112 are determined in accordance with the densities of the threads in the fabric structure. For example, when the warp density amounts to 70 ends/inch and the weft density amounts to 40 picks/inch, the width of the slit 112 is in a range 0.3 through 0.5 mm, and the length thereof is about 10 mm.

The second embodiment of the weft-image selector mechanism is shown in FIG. 4. This embodiment is particularly suited for use on looms of small weaving width. In the case of such looms of small weaving width, the advancing courses assumed by the weft under picking are in general inclined considerably against the direction of the cloth fell. Taking this fact into consideration, the weft-image selector mechanism shown in FIG. 4 has a bottom lid 111 provided with an X-shaped slit 113. This shape of the slit 113 meets the crossed courses 8a and 8b which are assumed ,by the weft 8 at the time of picking motion, i.e. the courses considerably inclined against the cloth fell.

The third embodiment of the weft-image selector mechanism of the present invention is shown in FIGS. SA and 5B. In the case of this embodiment, the weft- I image selector mechanism is in the form of a bottom lid 111 disposed to the open bottom end of the casing 109 and a column-shaped convex lens 114 incorporated in the bottom lid 111. As shown in FIG. 5B, the convex lens 114 is elongated in the direction of the weft courses 8a and 8b at the time of the picking motion. Due to the convexity of the lens 114, the imageof the weft arrives at the photoelectric cell 107 in an enlarged state.

When a long distance is needed for this optical enlargement, the light receiver 104 may advantageously be so structured that the course of the beam after passing through the lens 114 can be properly refracted. I

In the actual use of the photoelectric type weft sensor of the present invention, the sensing operation is carried out at a moment in the loom crank cycle close to the top dead center position. That is, when the top dead center is taken as the starting position-of the loom crank cycle, the sensing operation takes plce in a region of 350 through 35 of the crank angle. This period corresponds to the time when the lathe is positioned around the middle of its swinging stroke. At this very moment, the warp shed is closed as shown in FIG. 2, the weft 8 is caught by the warp sheets 16a and 16b, and the movement of the weft towards the cloth fell 17 is considerably lowered, which disposition is suited to the sensing operation of weft breakages. Separately from the above-described arrangement, suitable synchronizing pulses are produced at a moment corresponding to the top dead center of the crank cycle and are given to the later-described discrimination circuit also. 1 a

One typical embodiment of the mechanism for producing such synchronizing pulses is illustrated in FIGS. 1 and 6, in which a circular disc 116 or a like member is fixedly mounted on the tappet shaft 2 and is provided with a window 117 extending therethrough. A light source element 119 carried on a common arm 118 is positioned on one side of the disc 116 and a photoelectric cell element 121 is on the other side thereof. The relative arrangement of the window 117. and the elements 119 and 121 is so designed that the window 117 traverses the light beam emitted from the element 119 at a moment corresponding to the top dead center of the crank cycle. In other words, at every moment of the crank cycle top dead center, the light from the light source element 119 is received by the photoelectric cell element 121 so as to produce corresponding synchronizing pulses, which are given to the abovedescribed discrimination circuit via electric connections. The arm 118 is fixed to a suitable stationary part of the loom framework.

One typical embodiment of the above-mentioned discrimination circuit is illustrated in FIG. 7, in which the photoelectric cell 107 of the light receiver 104 (see FIG. 2) is connected to a gate circuit 124 via an amplifier circuit 123. This gate circuit 124 is connected to a flip-flop circuit 129 via a shaping circuit 126, a differentiation circuit 127 and a rectifier circuit 128. Separately from this, the photoelectric cell element 121 of the synchronizing pulse producing mechanism is connected to a shaping circuit 132 via an amplifier circuit 131. The output terminal of the shaping circuit 132 is firstly connected to the input terminal of the gate circuit 124. The output terminal of the shaping circuit 132 is secondly connected to a rectifier circuit 136 via an inverter circuit 133 and a differentiation circuit 134. The output terminalof the rectifier circuit 136 is also connected to the input terminal of the flip-flop circuit 129. The output terminal of the shaping circuit 132 is thridly connected to an inverter circuit 141 via a differentiation circuit 137, a rectifier circuit 138 and a one-shot-multi-vibrator circuit 139. The output terminals of the flip-flop circuit 129 and the inverter circuit 141 are both connected to input terminals of a NOR circuit 142, which is further connected to an operation terminal 144 via a relay circuit 143. In the present case, the operation terminal 144 is in the form of a mechanism for stopping the running of the loom. In the illustration, signals transmitted from element to element are designated with alphabetic letters. Although detailed structures are not specifically shown in the drawing, the component circuits of the discrimination circuit are of 4 conventional types which are generally known to persons skilled in the art. For example, the differentiation circuits are given in the formv of the socalled RC circuits of proper time constant RC.

The photoelectric type weft sensor of the present invention having the above-explained structure operates in the following fashion.

When the warp shed is open, the shuttle 7 flies along the upper face of the lathe 6 from a shuttle box on one side of the loom towards a shuttle box on the other side of the loom. The lathe 6 assumes the disposition shown in FIG. 8A around the time when the shuttle is received in the shuttle box on the receiving side. In this disposition, the weft assumes one of the courses 8a or 8b shown with chain-and-dot lines in the drawing and, in either case, the course is inclined against the cloth fell 17. About the time corresponding to the vicinity of the top dead center of the crank cycle, the lathe 6 assumes the disposition shown in FIG. 8B and the warp shed is closed so that the inserted weft 8 will be caught by the warp sheets 16a and 16b as shown in FIG. 2. In this disposition, the weft course 8a or 8b runs across a zone right under the weft-image selector mechanism 106 of the light receiver 104.

When the weft 8 runs across this zone, the light emitted from the light emitter 102 is temporarily intercepted by the weft 8 and the intensity of the light arriving at the photoelectric cell 107 through the weftimage selector mechanism 106 is accordingly reduced. This presence of the weft 8 can be very successfully sensed by the weft sensor of the present invention due to the excellent weft-image pick-up function possessed by the weft-image selector mechanism 106. This sensing can be accomplished regardless of the disturbance caused by the constant presence of the warp sheets.

The process of fashioning electric pulse signals in the discrimination circuit will now be explained indetail with reference to FIGS. 7, 9A and 9B. In FIGS. 9A and 9B, the abscissa designated two full revolutions of the loom crank. The wave-form A shows the output signal from the light receiver 104. The wave-form A includes a negative pulse a when the presence of the weft 8 is sensed. In case the weft 8 is absent at the very moment of the weft sensing, thewave-form A does not include such a pulse. This situation is seen in the second revolution of the loom crank. At the time of the beating motion, thelight emitter 102 incorporated in the lathe 6 comes under the fabric 18, i.e. the intensity of the light arriving at the light receiver 104, is temporarily reduced and this produces another negative pulse b on the wave-form A. Passage of the shuttle 7 produces still another negative pulse 0 on the wave-form A. It will be well understood that the two types of negative pulses b and 0 appear periodically once in every revolution of the loom crank. After amplification by the amplifier circuit 123, the wave-form A, incluidng such three types of negative pulses a, .b and c,is applied to the gate circuit 124.

Separately from this procedure, the synchronizing pulses produced periodically by the above-mentioned synchronizing pulse producing mechanism, e.g., the one shown in FIG. 6, are applied to the shaping circuit 132 after amplification by the amplifier circuit 131. The output wave-form F from the shaping circuit 132 is then applied to the gate circuit 124. Due to the gating operation by the gate circuit 124, the output wave-form B from the gate circuit 124 includes only pulses corresponding to the negative pulses a possessed by the wave-form A. By further passing through the shaping circuit 126, the differentiation circuit 127 and the rec-.

tifier circuit 128, the wave-form B is converted into the wave-form C, the wave-form D and finally into the wave-form E, which is applied to the flip-flop circuit 129 for the re-setting purpose.

The output wave-form F of the shaping circuit 132 is applied to the inverter circuit 133 and converted into the wave-form G, which is converted into the waveform J and the wave-form K by being processed through the differentiation circuit 134 and the rectifier circuit 136. This wave-form K contains negative pulses k which slightly precede the negative pulse(s) a of the wave-form A. The wave-form K of this shape is applied to the flip-flop circuit 129 for the setting purpose.

The output wave-form F of the shaping circuit 132 is further applied to the differentiation circuit 137, and converted into the wave-form H, the wave-form I, the wave-form N and finally into the wave-form O by being processed through the rectifier circuit 138, the one-shot-multi-vibrator circuit 139 and the inverter circuit 141. This output wave-form O of the inverter circuit 141 is applied to the NOR circuit 142. Between the two output wave-forms L and M, only the wave-form 

1. Photoelectric type weft sensing process on weaving looms comprising emitting light beams for sensing weft from one vertical side of a plurality of warp sheets forming a warp shed at a position about the middle of the lathe length in such a manner that said light beams advance across the course of the weft under picking, receiving said light beams on the other vertical side of the warp shed so that weft-images are clearly detected from an image caused by interruption of said light beam by said warp shed, converting photoelectrically said light beams so received into corresponding electric signals, subjecting said electric signals so obtained to an electric discrimination for identifying whether said weft exists or not at the time of a picking motion and interrupting the running of the loom only when said electric signals indicate the absence of weft at the time of picking motion.
 2. Photoelectric type weft sensing process as claimed in claim 1 wherein said light beams advance from upper side to underside of said warp shed.
 3. Photoelectric type weft sensing process as claimed in claim 1 wherein said light beams advance from under side to upper side of said warp shed.
 4. Photoelectric type weft sensor comprising, in combination, a light emitter located on one vertical side of a plurality of warp sheets forming a warp shed at a position about the middle of the lathe length with its light emitting and confronting the warp shed, a light receiver located on the other vertical side of said warp shed with its light receptive and confronting said light emitting end of said light emitter, at least one photoelectric cell incorporated within said light receiver, a weft-image selector mechanism incorporated in said light receiver for clearly separating weft-images from luminous images caused by said warp shed, a discrimination circuit for indentifying whether said weft exists or not at the time of a picking motion electrically connected to said light receiver and an operation terminal forming a part of said discrimination circuit for interrupting the running of the loom when the absence of weft at the time Of picking motion is sensed.
 5. Photoelectric type weft sensor as claimed in claim 4 wherein said light emitter is disposed in said lathe, said light receiver is disposed in the reed cap of the loom, said light receiver includes a cavitied casing and said weft-image selector includes a lid disposed to the light receptive side end of said casing and having one light passable window formed therethrough.
 6. Photoelectric type weft sensor as claimed in claim 5 wherein said window is in the form of a straight slit running in the weft direction.
 7. Photoelectric type weft sensor as claimed in claim 5 wherein said window is in the form of an X-shaped slit, each branch of which is parallel to one of the directions that wefts are inserted.
 8. Photoelectric type weft sensor as claimed in claim 5 wherein said discrimination circuit includes a gate circuit connected to said light receiver, a shaping circuit connected to said gate circuit, a differentiation circuit connected to said shaping circuit, a rectifier circuit connected to said differentiation circuit, a shaping circuit connected to a synchronizing pulse producing mechanism, a rectifier circuit connected to said shaping circuit via an inverter circuit and a differentiation circuit, a flip-flop circuit connected to said rectifier circuits, an inverter circuit connected to said shaping circuit via a differentiation circuit, a rectifier circuit and a one-shot-multi-vibrator circuit, a NOR circuit connected to said flip-flop circuit and to said inverter circuit and said operation terminal connected to the NOR circuit via a relay circuit.
 9. Photoelectric type weft sensor as claimed in claim 4 wherein said light emitter is disposed in the reed cap, said light receiver is disposed in said lathe of the loom, said light receiver includes a cavitied casing and said weft-image selector includes a lid disposed to the light receptive side end of said casing and having one light passable window formed therethrough.
 10. Photoelectric type weft sensor as claimed in claim 9 wherein said window is in the form of a straight slit running in the weft direction.
 11. Photoelectric type weft sensor as claimed in claim 9 wherein said window is in the form of an X-shaped slit, every branch of which is parallel to one of the directions that wefts are inserted.
 12. Photoelectric type weft sensor as claimed in claim 9 wherein said discrimination circuit includes a gate circuit connected to said light receiver, a shaping circuit connected to said gate circuit, a differentiation circuit connected to said shaping circuit, a rectifier circuit connected to said differentiation circuit, a shaping circuit connected to a synchronizing pulse producing mechanism, a rectifier circuit connected to said shaping circuit via an inverter circuit and a differentiation circuit, a flip-flop circuit connected to said rectifier circuits, an inverter circuit connected to said shaping circuit via a differentiation circuit, a rectifier circuit and a one-shot-multi-vibrator circuit, a NOR circuit connected to said flip-flop circuit and to said inverter circuit and said operation terminal connected to the NOR circuit via a relay circuit.
 13. Photoelectric type weft sensor as claimed in claim 4 for sensing wefts having a number of inserting courss defined by a trace of weft connecting a selvage of cloth to a shuttle running through an opened shed along the shuttle lathe, wherein said light emitter is disposed in said lathe, said light receiver is disposed in the reed cap of the loom, said light receiver includes a cavitied casing and said weft-image selector mechanism includes a lid disposed to the light receptive side end of said casing and having at least three light passable windows.
 14. Photoelectric type weft sensor as claimed in claim 13 wherein said lid includes three windows, one window of which meets the crossing point of two weft inserting courses and the remaining two of which are located on both sides of the first mentioned one aNd run parallel to the respective weft inserting courses.
 15. Photoelectric type weft sensor as claimed in claim 13 wherein said lid includes three windows, one window of which meets the crossing point of two weft inserting courses and the remaining two windows being located on both sides of the first mentioned window and running at at least partly including respective weft inserting courses.
 16. Photoelectric type weft sensor as claimed in claim 13 wherein said lid includes three windows, one window of which meets the crossing point of two weft inserting courses and the remaining two of which are located on one common side of the first mentioned one and run parallel to the respective weft courses.
 17. Photoelectric type weft sensor as claimed in claim 13 wherein said lid includes five windows, one window of which meets the crossing point of two weft inserting courses, the other two of which are lcoated on one common side of the first mentioned one running parallel to respective weft courses and the remaining two of which are located on the other common side of the first mentioned one running parallel to respective weft courses.
 18. Photoelectric type weft sensor as claimed in claim 4 for sensing wefts having a number of inserting courses defined by a trace of weft connecting a selvage of cloth to a shuttle running through an open shed along the shuttle lathe wherein said light receiver is disposed in said lathe, said light emitter is disposed in the reed cap of the loom, said light receiver includes a cavitied casing and said weft-image selector mechanism includes a lid disposed to the light receptive side end of said casing and having at least three light passable windows.
 19. Photoelectric type weft sensor as claimed in claim 18 wherein said lid includes three windows, one window of which meets the crossing point of two weft inserting course and the remaining two windows being located on both sides of the first mentioned window and running parallel to respective weft inserting courses.
 20. Photoelectric type weft sensor as claimed in claim 18 wherein said lid includes three windows, one window of which meets the crossing point of two weft inserting courses and the remaining two of which are located on both sides of the first mentioned window and run at least partly including respective weft inserting courses.
 21. Photoelectric type weft sensor as claimed in claim 18 wherein said lid includes three windows, one window of which meets the crossing point of two weft inserting courses and the remaining two of which are located on one common side of the first mentioned one and run parallel to respective weft courses.
 22. Photoelectric type weft sensor as claimed in claim 18 wherein said lid includes five windows, one window of which meets the crossing point of two weft inserting courses, the other two of which are located on one common side of the first mentioned one running parallel to respective weft courses and the remaining two of which are located on the other common side of the first mentioned window running parallel to respective weft courses.
 23. Photoelectric type weft sensor as claimed in claim 4 wherein said light emitter is disposed in said lathe, said light receiver is disposed in the reed cap of the loom, said light receiver includes a cavitied casing and said weft image selector mechanism includes a lid disposed to the light receptive side end of said casing and having two windows, one of which is positioned on the side of the lid toward the reeds of the loom and the other of which is positioned on the cloth fell side of said lid.
 24. Photoelectric type weft sensor as claimed in claim 23 wherein said discrimination circuit includes a discriminator connected to a photoelectric cell of said one window, a differential rectifier circuit connected to said discriminator via an integration circuit and a discriminator, a discriminator connected to a photoelectric cell of said cloth fell side window an inverter circuit connected to this discriminatoR, a gate circuit connected to this inverter circuit and to said first mentioned discriminator, a flip-flop circuit connected to this gate circuit and to said differential rectifier circuit a differential rectifier circuit connected to said second mentioned discriminator, an AND circuit connected to this differential rectifier circuit and said flip-flop circuit and said operation terminal connected to this AND circuit.
 25. Photoelectric type weft sensor as claimed in claim 4 wherein said light emitter is disposed in the reed cap of the loom, said light receiver is disposed in said lathe, said light receiver includes a cavitied casing and said weft-image selector mechanism includes a lid disposed to the light receptive side end of said casing and having two windows, one of which is positioned on the side of the lid toward the reeds of the loom and the other of which is positioned on the cloth fell side of said lid.
 26. Photoelectric type weft sensor as claimed in claim 25 wherein said discrimination circuit includes a discriminator connected to a photoelectric cell of said one window, a differential rectifier circuit connected to said discriminator via an integration circuit and a discriminator, a discriminator connected to a photoelectric cell of said cloth fell side window an inverter circuit connected to this discriminator, a gate circuit connected to this inverter circuit and to said first mentioned discriminator, a flip-flop circuit connected to this gate circuit and to said differential rectifier circuit a differential rectifier circuit connected to said second mentioned discriminator, an AND circuit connected to said differential rectifier circuit and said flip-flop circuit, and said operation terminal connected to this AND circuit.
 27. Photoelectric type weft sensor as claimed in claim 4 wherein said light emitter includes a cylindrical casing fixed to a part of the loom, a convex lens disposed at the light emitting end of said casing, a cap inserted over said casing on the other side and a lamp carried by said cap with its filament being registered at the weft direction.
 28. Photoelectric type weft sensor as claimed in claim 4 wherein said light emitter is fixed to the reed cap and said light receiver is movably mounted in a recess of the lathe.
 29. Photoelectric type weft sensor as claimed in claim 28 wherein said light receiver is accompanied by an actuating mechanism and said light receiver moves forwardly out of said recess and rearwardly into said recess being actuated by the swing movement of the lathe via said actuating mechanism which includes a fixed cam and a cam follower roller connected to said light receiver.
 30. Photoelectric type weft sensor as claimed in claim 28 wherein said light receiver is accompanied by an actuating mechanism and said light receiver moves forwardly out of said recess and rearwardly into said recess being actuated by the rotation of the tappet shaft via said actuating mechanism which includes an actuator cam, a slider and its related assembly accompanying said light receiver and a transmission mechanism between said cam and said assembly. 